Visualization's Next Frontier

by Mark Taylor and Steve Moler

Visualizations like this one of the 790-foot (241-meter) Foothills Parkway Bridge 2 in Blount County, TN, can help project managers and stakeholders see how a transportation facility will interact with its environment.

The time has come for this design tool to advance from use as a conceptual exhibit to full integration into the project development process.

Highway design engineers traditionally have learned to analyze and solve problems in two dimensions (2-D). From basic drafting classes in high school to mathematics and engineering coursework in college, engineers learn to solve problems by simplifying the world into 2-D. Complex objects and concepts become 2-D cross-sectional views, drawings, blueprints, renderings, and maps. These representations, however, lack the information necessary to fully understand how a project will perform in the real world.

Increasingly, engineers can synthesize all such 2-D data into various types of three-dimensional (3-D) and dynamic (animated or real-time simulation) four-dimensional (4-D) models, renderings, animations, and simulations. Advances in personal computing and development of computer-aided design and drafting (CADD) have helped put a new approach--design visualization--directly into the hands of highway designers.

"The 2-D way of thinking and drafting-centered approach to project development limits the designer's level of creativity and analysis," says Patrick Hasson, team leader for the Federal Highway Administration's (FHWA) Resource Center safety and design technical service team. "Too often the 2-D approach results in costly rework and design changes late in the process, as potential problems are discovered. Design visualization changes all of this. The model-centric design approach allows the model to be continuously updated as simulations and analyses are performed, multidisciplinary input is added, and the final design evolves."

For years, transportation practitioners have used 3-D computerized renderings and animation to convey conceptual designs to decisionmakers, stakeholders, and communities during the public involvement phase of transportation projects. But now agencies are pushing design visualization to the next level, taking it beyond public involvement and integrating it into the entire project development process, from early conceptualization to final design and even actual construction.

"Design visualization has been used in various ways as a highway design tool for many years," says King Gee, associate administrator for FHWA's Office of Infrastructure. "But its use has tended to be limited to the public involvement process and to large, complex, and high-profile projects. Not anymore. We see visualization as an opportunity to improve the entire planning, design, and construction process for all types of projects, big and small, and from start to finish."

Many Technologies

Fortunately, there is no shortage of technologies to help transportation engineers develop design visualizations.

Aerial photogrammetry is the science of making reliable measurements by using survey-controlled aerial photography and has been in practical use for a century. Cartographers combine aerial photography with camera data and the positions of targeted ground survey points, visible in the photographs and measured on the photographic image, to produce topographic maps and elevation data for digital terrain models. The cartographers digitally scan the aerial photographs and rectify them analytically to produce 2-D imagery that shows length and distance to scale.

To develop design visualizations, engineers merge the proposed design model with the existing ground digital terrain model and photo imagery. Important to visualization, aerial photogrammetry can provide high-quality and accurate imagery that designers can drape onto the model surface to provide a photo-realistic 3-D visualization or animation.

Light detection and ranging (LiDar) is a remote sensing system that simultaneously collects topographic data and digital imagery. A LiDar sensor pulses a narrow, high-frequency laser beam toward the ground and determines distance by recording the time difference between emission and return of the reflected signal.

LiDar sensors can operate from fixed-wing aircraft, helicopters, or a tripod on the ground, depending on the coverage area and density of points and precision needed. LiDar methods gather many more ground survey points than traditional ground-based surveys and with less interference and exposure to traffic. For visualization, LiDar can collect a wealth of topographic data in a short time and can obtain detailed elevation data and imagery with accuracy and realism. (See "Virtual Highways--A Vision of the Future" in Public Roads, May/June 2007.)

To obtain greater vertical accuracy for finer scale highway design and construction work, engineers must augment GPS data with lasers or other methods. GPS technology offers engineers using visualization the ability to measure and locate in the field the position of any existing or design feature anywhere in the 3-D design surface model.

Geographic information systems (GIS) are databases used to manage and present data linked to a certain location. They can store, query, analyze, and overlay a variety of geospatial information in a visual, map-oriented framework. Engineers can integrate GIS information directly with highway CADD data for use in visualizations. For example, they can overlay environmental information onto a design model together with aerial photography.

Engineers typically use GIS for areas larger than the highway corridor, and it normally does not provide the high level of detail needed for final design and construction. GIS data are cost efficient to obtain and effective for use in conceptual and preliminary design.

This visualization of New Mexicoâ€™s Rail Runner Express commuter rail project enabled the design team to see what the work looked like at any point during the project. The tool also helped reduce design errors and identify conflicts that could have affected construction costs and schedules.

Virtual global maps include various software products, such as GIS, and the capability to directly access multiple online sources of imagery, topographic maps, and gridded terrain data. Map software can access a variety of geospatial data, such as data from the U.S. Geological Survey's Watershed Management System, as well as elevation data and color imagery for the entire world. The software also can view elevation data in 3-D with any loaded raster (scanned) imagery and vector (line) data draped on top.

The elevation data and imagery of most virtual global map systems are not accurate enough for use in final design or construction, but can help primarily in conceptual and preliminary design. The commercially available information can be more cost effective and beneficial than project-specific survey and mapping in the early stages of a project or than doing without. The output of highway CADD software can interface with many virtual global map products, producing an alternative platform for visualizing and evaluating designs in larger contexts.

Three-dimensional highway design modeling software is highly specialized engineering software for calculating and drafting highway geometrics and associated design features such as volumes of materials. Embedded in the software are geometric design criteria and methodologies developed by the American Association of State Highway and Transportation Officials (AASHTO) applied by computer to automate complex engineering calculations and help designers make decisions.

Modern 3-D modeling capabilities have evolved over two decades from traditional 2-D based CADD software into comprehensive highway engineering methodology and include highway design modeling, design visualization, and some forms of animation. Data from 3-D highway design models can be output to interface with more specialized 3-D software applications. Having the capability for 3-D highway design modeling and visualization combined with the software used for traditional 2-D engineering design and drafting is critical for efficient, effective applications of visualization in the design process. The combined capability enables designers to use both 2-D and 3-D techniques on the same project and become proficient with the 3-D modeling and visualization functions through day-to-day experience.

Four-dimensional traffic simulation visualization provides the capability to view traffic information that is output from various traffic analysis tools, overlaid onto a 3-D design surface model, and displayed as animation. The visualization consists of traffic flow information depicted by various icons representing the types of vehicles in the traffic stream, bicyclists, and pedestrians. The level of realism can range from basic shapes, such as rectangles and circles in a wireframe model, to fully rendered vehicles and people in a highly realistic virtual environment.

The visualized traffic flow information can range from parameters of the collective traffic stream to data on individual traffic elements--for example, vehicles and pedestrians--output from software simulating microscopic traffic flow. Microscopic simulation, or microsimulation, models each entity, such as cars and people, versus averaged variables such as flow rate and density. The types of visualized roadways can include intersections, streets, multilane roadways, freeways, and interchanges.

The traffic analysis tools can transmit the data to the 2-D rendering or other specialized 3-D modeling software, or the traffic elements are modeled automatically in 3-D by the traffic analysis software. Visualizing the traffic simulation enables designers to evaluate the traffic performance of the design within the perspective of the virtual 3-D design model, instead of evaluating either the traffic simulation numerical data or the shape of the design model separately and in isolation from each other.

The result of combining visualization of the output from the traffic microsimulation model with the 3-D design model is an animation or real-time simulation that realistically demonstrates not just how the facility will look, but more important, how it will operate under future design traffic loading conditions and within local contextual settings. The 3-D simulation of moving vehicles becomes especially useful and adds value to the design process when the combined physical and traffic element models are visualized and experienced from the driver's perspective operating within the stream of traffic.

Automated machine guidance (AMG) is the integration of digital surface data with precise positional information onboard construction machinery. In conventional construction, the numerical dimensions for depths, widths, and slope ratios are available only at stakes driven into the ground. The operator interprets the numerical data, and construction relies solely on that judgment for guidance of the machinery between stakes. With AMG, however, the operator relies on onboard 3-D design surface modeling and computer-assisted or automated controls of the cutting blades to construct the roadway instead of interpreting stakes in the ground and operating the cutting blades manually.

Various geospatial technologies, including GPS, laser augmentation, robotic total stations, or combinations of these, provide the precise onboard positional information. The equipment directly uses, and visually displays for the operator, continuous 3-D spatial information about the relationship of the machine's cutting blade to the design surface.

Adobe® Acrobat® 3-D file viewer is a feature of the software's interactive display. Common CADD software can convert a 3-D design model into a PDF document with the 3-D design file incorporated into it. A designer can interact with the model or play a predefined animation that was set up in the design program. Important for visualization, this capability enables designers to view the 3-D design model outside the CADD software in other applications that use a PDF format and to send 3-D interactive views of the project to anyone who has Acrobat Reader, a free utility.

These computer renderings of a Utah highway overcrossing illustrate how visualization can show different materials used on structure walls. This capability is useful in pursuing context sensitive solutions and obtaining feedback from the public.

Virtual design and construction (VDC) is the integrated use of multidisciplinary performance models for the project delivery process. The disciplines can include design, construction, and project management. VDC combines engineering models of the physical facility, the project delivery process, and the organization of entities doing the work. These virtual models are linked to access shared data so that changes to one aspect alter dependent aspects of the related models. The resulting combined system often is called a building information model, or BIM. In that model, VDC links data about the facility and its components plus analysis of the delivery schedule, cost, 4-D (spatial and temporal) interactions, and risks. VDC uses 2-D, 3-D, and 4-D modeling and visualization methods to depict these interactions.

VDC also can be used to integrate cost-based business metrics and strategic management measures. Specialized VDC software tools and methodologies developed in recent years can integrate with common highway design software. Architects have used VDC successfully for analysis, optimization, and management of the delivery of buildings and other vertical projects, but it is just emerging as an application on linear transportation projects.

Visualization's Many Benefits

The highway design industry, in facing its many challenges, is looking for better methods to produce high-quality work while accelerating project schedules, meeting deadlines with fewer staff, and lowering project development and delivery costs. Visualization offers the highway design engineer--and ultimately the public--numerous benefits. In addition to enhancing public involvement, visualization enables engineers to examine their own concepts from multiple viewpoints, including some that are impossible with traditional 2-D plans.

Visualization is an effective method for performing quality control and verifying quality assurance. When an engineer visualizes a design model in 3-D, the interaction of design elements is more apparent. The engineer can identify and better communicate anomalies and conflicts that are embedded within the design, such as inconsistent slopes, relationships with structures, drainage problems, and utility conflicts.

Several projects using the design-build contracting method have adopted visualization to expedite delivery and reduce cost. In the design-build method, cost savings have more direct rewards than in the traditional design-bid-build approach.

An example is New Mexico's Rail Runner Express commuter rail project that connects Belen, Albuquerque, and Santa Fe along a corridor generally following I-25. The New Mexico Department of Transportation (NMDOT), in cooperation with the design and construction contractors, completed the Albuquerque-Santa Fe section in December 2008. The design firm used a 3-D modeling system during and after the bid process, enabling the design team to bring up plans and views and critique them in different offices in real time.

"Our 3-D model was instrumental to the team's success," says Tim Cobb, the firm's design manager. "We collaborated among all parties and identified solutions in real time before a design package was actually submitted to the NMDOT."

The model, which used road-building software, enabled viewers to see what the work looked like at any point in time. The model helped reduce design errors and identify conflicts that could affect construction costs and schedule," says Kevin O'Connor, the design firm's managing engineer for CADD applications. "People could look at a screen and reach an agreement on changes. Every element was interactive. For instance, if there were custom-grading areas needed around bridges or other structures, the model could identify that immediately."

Another benefit is that visualization enables project managers to assess a wide range of project alternatives and design options visually. Better analysis of alternative conceptual and preliminary designs can lead to cost savings through such processes as value engineering, especially if used early in project development. Value engineering is a review or analysis of a project to identify and recommend alternative solutions that reduce life-cycle costs while adding value to the project.

The Florida Department of Transportation used visualization for a value engineering study of the Okeechobee Road (U.S. 27) project, a six-lane, controlled access highway in central Florida. Project managers wanted to avoid the common problem of not having enough information early in the project to make good decisions based on facts. To help fill the data gap, the team used various visualization techniques that helped elicit timely and pertinent comments from internal project team members, regulatory agencies, and the public. As a result, project managers did not miss any time-critical opportunities, and they identified important project flaws.

Visualization also can help planners and project managers identify and comprehend complex sequencing issues before construction begins, expose issues that otherwise might be unrecognized, and reveal potential cost savings in the staging of construction activities. Construction cost overruns tend to be attributed to design problems, which can be greatly reduced through 3-D CADD design and visualization of construction sequencing.

Eyeing Safety

A 3-D, model-centric approach enables designers to analyze safety issues from different perspectives than the traditional 2-D drafting-centered design approach--most important, from the perspective of the end user, whether a driver, bicyclist, or pedestrian. Among the advantages is enhanced analysis of linear or point-to-point sight distances for stopping, passing, intersections, and directional decisionmaking. Sight distance modeling also can measure how much of the critical surface area of the highway ahead is visible or obscured. Current software applications enable designers to measure linear sight distance continuously along the roadway and the visibility of approach roads, driveways, bicycle lanes, pedestrian crossings, and other potential conflict points. Software capable of automatically calculating and visually displaying these measurements is an important next step.

Transportation agencies soon will use visualization as a tool for road safety audits (RSAs) during preconstruction planning. An RSA is a formal examination of the safety performance of an existing or future road or intersection by an independent, interdisciplinary audit team. RSA teams typically visit project sites to view existing conditions firsthand but must rely on interpreting 2-D drawings to assess safety issues of proposed design improvements. Most RSA team members are not design engineers and therefore are not highly skilled at interpreting detailed drawings. Visualization helps the team better understand the design and the user's perspective.

Visualization can provide designers with a host of other advantages. Unlike 2-D modeling, visualization includes parameters that enable designers to analyze combinations of horizontal and vertical alignments and cross-sectional elements, intersection designs, ramp terminals, turning paths at intersections, and traffic performance. Visualization can help optimize visibility-related design decisions, thus helping designers make it easier for users to perceive and respond to visual cues and information embedded in the geometric design and provided in the signing and marking.

EFLHD engineers used common highway engineering CADD software to begin this visualization. Then they imported the terrain and bridge into photo editing software, merging the two files and adding the trees and cars.

Adequate sight distance and visibility is a critical element in navigation and safe operation. Visualization can help designers provide users with additional levels of visibility at key locations, which is particularly important for older drivers or pedestrians who need additional time to perceive and react to changes in the roadway configuration and traffic conditions.

Visualization is an important tool for helping designers ensure that the physical layout of a roadway is recognizable to drivers, bicyclists, and pedestrians, and intuitive to navigate. By applying 3-D modeling and visual analysis, design engineers can reduce some of the complexity of interchanges and intersections and make them easier to recognize and maneuver through, leading to safer and more efficient operations.

"Imagine designing a complex interchange and then having the ability to drive through that interchange in a simulator to test your ideas and concepts," says FHWA's Hasson. "Visualization allows you to evaluate vertical and horizontal alignments, traffic flow, sight distances, signage, and even aesthetics before you go to the next project phase. That's what visualization can do for the highway designer and the end user."

Visualization is also useful in pursuing context sensitive solutions (CSS), a collaborative, interdisciplinary approach that seeks to integrate a transportation facility seamlessly into its environment while meeting safety and mobility goals. For decades, a short section of scenic Route 1 in San Mateo County, CA, south of San Francisco, kept sliding into the ocean because of severe slope instability. After many studies, the California Department of Transportation (Caltrans) decided to bypass the unstable section by constructing a 4,000-foot (1,219-meter) tunnel through an adjacent environmentally sensitive mountainside.

To help explain the proposed Devil's Slide Bridges & Tunnels Project to the California Coastal Commission, which initially opposed the project, Caltrans used visualization to show how the tunnel would blend into California's coastal landscape. The commission had rejected an earlier design primarily for aesthetic reasons, particularly at the tunnel portals. Working with visualization technicians and design engineers, Caltrans revised the design to better match the surroundings. The department developed several new designs for the commission to evaluate. The commission eventually approved the project, which is now under construction.

A Novel Interchange

Visualization served a critical function during design of a new type of U.S. interchange in Kansas City, MO. The Missouri Department of Transportation (MoDOT) needed to make operational and safety improvements to a busy urban interchange at I-435 and Front Street, which was burdened with heavy car and truck traffic during peak hours. In 2002, MoDOT evaluated four options, ultimately choosing a modified tight urban diamond design that met basic cost, capacity, and safety goals.

However, through a 2004 FHWA-sponsored workshop on geometric design, the MoDOT design team learned about a double crossover diamond (DCD) interchange (also known as a diverging diamond interchange, or DDI) in Versailles, France, that had a low crash rate over its 20-year history. A DCD requires drivers to briefly cross to the left side of the road between the two ramp terminals of a diamond interchange. At the first signalized ramp terminal, traffic crosses over to the left side of the road, travels over or under the freeway, and crosses back to the right side of the road at the second signalized ramp terminal. The unconventional crisscrossing pattern substantially reduces conflict points and increases the capacity of turning movements to and from freeway ramps.

This visualization shows how an interchange in Orem, Utah, would appear after construction of a flyover ramp.

The MoDOT design team created a traffic simulation model to compare the tight urban diamond with the DCD interchange. The results proved favorable for the DCD design. For example, the capacity of left-turn lanes doubled, eliminating the need for triple left-turn lanes. The design improved safety by allowing left turns onto the ramps that eliminate the crossing of opposing traffic and by improving sight distance at ramp terminals. Overall traffic performance improved dramatically because of the better turn-lane performance and shorter signal cycles. MoDOT estimated the DCD would cost half as much as the conventional interchange.

The design team concluded the DCD was a superior design, but with one concern: Because there were no operational DCDs in North America, drivers would be unfamiliar with the counterintuitive crossover movements. Viewed in 2-D, the design appears complicated and confusing. MoDOT design engineers wanted to do additional analysis before finalizing such a novel design.

FHWA's Human Centered Systems team at the Turner-Fairbank Highway Research Center (TFHRC) in McLean, VA, helped MoDOT build a simulation of the proposed DCD in FHWA's Highway Driving Simulator using 3-D and 4-D visualization. The simulation enabled MoDOT and FHWA engineers to drive through their own design using real-time, 3-D software. The Human Centered Systems team recruited more than 70 volunteers to participate in test drives through the simulated interchange.

The simulation revealed sight distance conditions at the DCDs that otherwise might not have been noticed; it also revealed unintended driver behaviors that resulted from the first attempt to mitigate the sight distance problems at traffic signals due to the curved roadway approach to the DCDs. One such behavior was drivers bearing right instead of left at crossovers. Other types of driver errors were no more likely with the DCD configuration than with a conventional interchange.

A follow-up simulation run using a revised design with improved geometrics, pavement markings, and signing showed that almost all concerns were unwarranted. For example, none of the participants bore right at any of the crossovers. Navigational errors were rare, and mean speeds were 23 miles per hour (mi/h) (37 kilometers per hour, km/h) at the DCDs, compared to 34 mi/h (55 km/h) at diamond interchange intersections. The lower speed at the DCDs may result in less severe crashes should they occur, and the lower average speed still will provide adequate flow and capacity due to elimination of the signalized left turn phases.

"The many insights we gained from this analysis would not have been possible without the simulation," says Thomas Granda, a senior psychologist at TFHRC and team leader of the Human Centered Systems team. "Letting MoDOT's engineers test their own designs, and then letting potential end users actually test-drive the proposed interchange early in the design process, gives us a tremendous tool to improve safety and operational efficiency before the facility is built, thereby eliminating the need to go back later and correct things. This is the value visualization brings to the table for the transportation design engineer, and ultimately the public."

The Road Ahead

As with any emerging technology, design visualization must overcome a number of challenges before becoming fully integrated into the entire project development process. The National Cooperative Highway Research Program (NCHRP) recently completed one of the most comprehensive studies of design visualization and evaluated those challenges.

NCHRP Synthesis 361: Visualiza-tion for Project Development involved detailed interviews with leading organizations that are developing and incorporating visualization into the preconstruction component of project development. State DOTs, FHWA, universities, and consultants completed detailed questionnaires on a variety of visualization issues, including standards, best practices, training, staffing, resources, and how and why visualization is being used.

The study found the lack of visualization standards and guidelines to be the biggest challenge, making it more difficult to formally integrate related technologies into the design process. None of the 11 organizations contacted for Synthesis 361, including FHWA, had official visualization standards, guidelines, or policies. Another publication, AASHTO's Visualization in Transportation, explains in general terms why and how the technology is used. The AASHTO guide provides a primer for use of the visualization technology in the project development process, the various types of visualization products that can be generated, benefits and constraints, and a glossary of commonly used terms. The guide was important for unifying the industry nomenclature to describe the various types of products and their uses.

Synthesis 361 showed that visualization tends to be an independent, grassroots process that occurs at the end of the preliminary design or public involvement phases. "Once a preferred alternative selection is made, the final design phase begins and the use of visualization ends," the authors of the study concluded. Ideally, visualization should continue so that engineers can modify and enhance visuals for use in the final design phase.

Organizations contacted for Synthesis 361 said they would like to see a national set of guidelines that they could tailor to their individual needs. National standards and guidelines could cover issues such as how to use visualization from the beginning to the end of a project; how to recruit, train, and sustain visualization staff; and how to fund visualization in the overall project budget. Practitioners need such standards if visualization is to become a viable discipline within the design process, the study found. The guidelines should be basic and written for project managers and other decisionmakers, and should include the tools available, benefits of using each tool, typical production schedules, associated costs, and considerations for developing budgets.

Visualizations such as this one of Tennesseeâ€™s Foothills Parkway Bridge 2 are helpful for achieving context sensitive solutions.

Cost-Benefit Analysis

The lack of national standards and guidelines produces a trickle-down effect into other areas and additional challenges for advancing visualization technologies. One challenge is the lack of cost-benefit analysis for visualization. Synthesis 361 found that not enough has been done in this area to demonstrate visualization's value to the overall design process.

With the possible exception of the Utah Department of Transportation (UDOT), no State DOT that participated in the study has completed detailed cost-benefit analyses of its visualization efforts. For example, in California, Caltrans used visualization extensively on the Devil's Slide Bridges & Tunnels Project, but the department has not completed a cost-benefit analysis.

UDOT has measured dramatic cost and productivity savings on projects that use visualization. For example, the department saw reduced change orders, construction cost savings, and more efficient use of materials as a result of its visualization efforts on the Hurricane Arch Bridge project over the Virgin River in southwestern Utah. According to Synthesis 361,UDOT's cost-benefit analysis estimated a 15:1 return on investment on projects that use visualization tools.

"The principles that we discovered during this process led us to believe that the value of 3-D design and visualization [is] not just as tools for large, very complex projects, but.would bring us significant value on almost every project," wrote UDOT Engineering Technology Support Manager Greg Herrington in the study questionnaire.

This simulation of a double crossover diamond interchange enabled MoDOT and FHWA engineers to drive through their own design, and 70 volunteers also took test drives through the simulated interchange.

The Minnesota Department of Transportation (Mn/DOT) established a formal visualization unit in the mid-1990s, complete with startup budget and centralized standards and guidelines, job descriptions, and the like. The unit provided statewide visualization services until 2003, when it was disbanded amid budget cuts. "This cost-cutting measure was partly enacted because there was not a clear cost-benefit analysis in place for the use of visualization technology as a central office function," according to Synthesis 361.

The Transportation Research Board's (TRB) Visualization in Transportation Committee currently is investigating quantification of costs and benefits, or return on investment, of visualization. The committee is compiling project case studies to measure the typical costs and estimated benefits for various project types and visualization techniques. TRB anticipates the results will be available in mid-2010.

Training

Another challenge facing transportation agencies as they deploy visualization technologies is training. Synthesis 361 found that visualization training has been limited to mentoring, self-teaching, periodic workshops, and vendor on-the-job demonstrations.

No national training program exists within the transportation community for visualization, nor does the National Highway Institute, FHWA's training unit, offer any courses. At Caltrans, for example, there are no formal training classes for visualization; instead, periodic seminars and classes are offered for particular software applications. Visualization specialists and design engineers attend these sessions and then pass down the information to colleagues. At Mn/DOT, many visualization technicians come from universities and art schools that teach 3-D applications. All the other State DOTs reporting in Synthesis 361 noted that they offer no formal visualization training programs.

FHWA's EFLHD conducts mainly in-house training, through mentoring. EFLHD also publishes the Design Visualization Guide, which introduces visualization tools and innovative practices to Federal Lands Highway (FLH) designers for use in FLH projects as needed. The guide helps designers learn to use commonly available software tools to produce visualizations.

As concluded in Synthesis 361, the lack of formal visualization training can be attributed to several factors. Significant investment is needed to train people to use visualization technologies. Limited State DOT budgets have curtailed training and professional conference attendance. The wide variety of visualization software packages makes delivery of standardized training more difficult. Also, visualization requires high skill levels. For example, UDOT estimates that the average visualization trainee requires several additional months of on-the-job training to become fully proficient.

Utah used this visualization to show how the new Hurricane Arch Bridge over the Virgin River would appear.

Staffing

Another significant challenge is staffing transportation agencies with specialists and designers skilled in visualization. A lack of qualified specialists has hindered development of visualization at the agencies studied in Synthesis 361. Finding employees with an appropriate combination of design, CADD, and artistic or landscape architecture backgrounds is sometimes difficult.

Most of the DOTs in Synthesis 361 did not have formally recognized visualization departments. DOTs tend to incorporate visualization into other departments, such as landscape architecture or structural design. At Caltrans, for example, visualization is housed under the landscape architecture and structural architecture disciplines. At the New York State DOT, visualization is part of the Office of Design's landscape architecture program.

As engineers apply visualization more extensively, are separate, independent departments needed? Synthesis 361 found that the presence of recognized visualization departments enabled measurement of budgeting, expenses, and staff-hour requirements. To integrate visualization directly into design practice, agencies must embed workflows into the CADD processes performed by design engineers.

Budgets

Another challenge for visualization
is budgeting and funding. Most agencies cited in Synthesis 361 said they do not have specific budgets for visualization. Instead, they typically incorporate visualization into project budgets. There is no ongoing budget for visualization at UDOT or Mn/DOT, for instance, and Caltrans has no formal budget for hardware, software, or staff hours for visualization.

Adapting to Change

The final challenge in fully integrating visualization into the entire project development process is dealing with change itself. "The traditional approach to highway design in which we develop static 2-D plans, profiles, and cross sections is deeply embedded in the design engineer's culture and our organizations," says FHWA's Hasson. "This approach is a holdover from the T-square, pen-and-ink, and blueprint era. Now we are asking our industry to learn entirely new technologies and new ways of doing things. It's not that easy to reverse decades of doing things a certain way, and to retool, reinvest, and restaff for a new approach."

However, to address the safety and congestion issues facing the Nation, design engineers need better analytical tools. Visualization can be one of them. New workflows involving 3-D modeling and design visualization now are supplementing and ultimately might supersede many of the 2-D, drafting-centered approaches practiced for decades.

Tom Norton, former executive director of the Colorado DOT, reiterated the difficulty of change at the 5th International Visualization in Transportation Symposium and Workshop. "We've got a lot of engineers who have been around 20 to 30 years, and they think they know how to do it [design]," he says. "They've been doing it that way for a long time, and that's all they want to do. I've had a tough time convincing people that the only real constant in their life at the DOT is change itself."

Early adopters of the 3-D modeling and visualization approach are leading the design and construction industry by demonstrating cost savings and enhanced quality. Taking visualization to the next level will require the transportation industry to establish national standards with guidelines for its application, design analysis, budgeting, training, and staffing. Additional research should quantify visualization's cost and benefits and should determine how it helps the designer and, ultimately, end users--the traveling public. As this happens, visualization will indeed reach the next frontier.

The NCHRP report Synthesis 361 found that State DOTs have difficulty finding employees who can meld CADD, visualization, artistic, and landscape architecture backgrounds to produce visualizations such as this one for the Blount County, TN, project.

Mark Taylor is a safety and geometric design engineer with FHWA's Resource Center in Lakewood, CO. He has been with FHWA since 1974. After graduating from the agency's Highway Engineer Training Program, he served as assistant area engineer in the Arkansas Division and then in a variety of positions with the Central Federal Lands Highway Division, including project development engineer. He also served as the design discipline leader for FLH. He has a B.S. in civil engineering from Virginia Polytechnic Institute and State University.

Steve Moler is a public affairs specialist at FHWA's Resource Center in San Francisco. He has been with FHWA since 2001, assisting the agency's field offices and partners with media relations, public relations, and public involvement communications. He has a B.S. in journalism from the University of Colorado at Boulder.

For more information and resources regarding design visualization, visit www.trbvis.org/MAIN/TRBVIS_HOME.html, or contact Mark Taylor at 720-963-3235 or mark.taylor@dot.gov, or Steve Moler at 415-744-3103 or steve.moler@dot.gov.

Visualization Tools

Physical models are an old tool that continues to be valuable for conceptual design visualization and quick evaluation of basic design surfaces. Engineers can easily assemble models from patterned 2-D media such as paper, cardboard, foam board, and balsa wood. Surfaces can contain photo images, colors, or textures to add realism. Physical models are portable, easily manipulated, and a tactile visualization alternative to electronic media.

Hand renderings are another early tool, providing instant visualization with freehand sketches or tracing over maps or CADD drawings for quick development of concepts and alternatives. Manual creation of geometric designs can be faster and more intuitive than CADD drafting tools, and enables engineers to mentally balance numerous complex design concepts simultaneously. Designers can create manual drawings on electronic "smart boards" or scan them electronically and attach and scale them for referencing to 2-D CADD files.

Computer 3-D graphics are perspective views generated by engineers after developing 3-D models of designs. Designers can visualize surfaces by constructing virtual models using wireframes or can render them by using basic colors and textures or draped imagery. Most highway CADD software includes basic modeling and rendering capabilities. Specialized software can add effects and realism such as lighting and shading. Three-dimensional graphics provide virtual "real-world" perspectives of surface models for evaluation. Specialized design techniques and software can automatically generate complex 3-D measurements and enable designers to determine the extent of visibility of road surface for evaluation of roadway and intersection sight distances.

Computer animation is a series of closely spaced 3-D views of a surface model following a designated orientation and path and joined to create a moving image. Animations include the fourth dimension: the passage of time. Designers use animation to simulate the live movements of motorized vehicles, bicyclists, and pedestrians through a 3-D model. Animation is necessary to simulate the dynamics of traffic operations and transportation facilities in actual service from road users' perspectives. Animation can help designers evaluate how long design elements will remain visible to users while they are moving through the traffic stream, the existing and designed perception-reaction time, and overall driver workload.

Real-time simulation is a graphic database technology that provides interactive navigation through a 3-D model. Real-time simulation differs from animation in that the viewer is free to change the position, location, and orientation of the perspective view and zoom in or out instead of following a designated orientation and path. The viewer can interact with objects in the 3-D model because it is a graphic database and thus can switch the depiction between various alternatives. Designers can animate individual objects within the 3-D model to simulate vehicle, bicyclist, and pedestrian traffic movements; traffic signal operations; or other activities and events. Combined with other real-time or scripted data, the simulation can enable designers to evaluate complex situations in operation and adjust the design to achieve optimal performance.